1. Field of the Invention
The invention relates to field of disk drives and more particularly to the writing of processes for making patterned media.
2. Description of the Related Art
As disk drive areal density continues to increase, media pre-patterned during manufacturing has been proposed to xe2x80x9cpre-recordxe2x80x9d servo information, to provide magnetic isolation of the tracks, or to even provide isolated magnetic xe2x80x9cbits.xe2x80x9d For example, U.S. Pat. No. 6,331,364 B1, describes forming isolated regions corresponding to bits in magnetic media by exposing a special alloy of iron platinum (Fe55Pt45) to ion irradiation with 700 keV N+ (or alternatively, helium, argon, neon, krypton or xenon) ions at doses of 2xc3x971014 to 2xc3x971015 ions/cm2. The ion bombardment is said to make the exposed material xe2x80x9csoft,xe2x80x9d i.e., the exposed material has less coercivity and is less able to retain magnetic remanence. The described process irradiates the media either through patterned non-contact stencils, or through patterned resist formed on the media. In either case, the patterning process is performed after the magnetic layers are deposited through a sputtering processxe2x80x94but before the conventional protective sputtered carbon overcoat and functional lubricant layers are applied.
One problem presented by patterning the media prior to depositing the protective carbon overcoat and is that the media is potentially exposed to contaminants, particularly oxidants, which can lead to corrosion and eventual failure of the disk. This problem is particularly acute when a patterned resist is used in the patterning process. The resist must be applied and/or removed outside the evacuated chamber in which the disk was sputtered. Further, the resist is typically removed using a chemical solvent. Both exposed to disk to contaminants.
If one employs non-contact stencils for patterning masks, such as disclosed in the ""364 patent, it may be possible to conduct the patterning process without removing the disk from the same sputtering environment. This reduces the contamination problem involving airborne contaminants. However, because the stencils is not directly contacting the disk, the feature size achievable using a stencil is significantly less than the feature size achievable by patterning through a contact resist. As areal density continues to increase, there is a need to develop a xe2x80x9ccleanxe2x80x9d resist patterning process.
An additional problem in the ""364 patterning process is presented by sputtering debris. This debris is characterized by very large asperities essentially composed of the material being sputtered. Unless this debris is removed prior to subsequent patterning process steps, the debris will cause localized failure of patterning. If severe enough, the disk will fail quality tests and will have to be scrapped.
Therefore, there is a need for a patterning process that permits the use of resist in the patterning process and that also provides for the removal of sputtering debris prior to patterning.
The invention comprises a process for making a patterned media disk including the steps of sputter-depositing one or more magnetic layers; sputter-depositing a protective overcoat layer; applying a lubricant on the protective overcoat layer; buff/wiping the lubricated disk to remove debris; and exposing the magnetic disk to an effective amount ion radiation through a mask to reduce magnetic remanence in selected portions of the disk.
In the one embodiment, the mask is a patterned resist applied to a carbon-overcoated disk after the buff/wiping lubricant has been removed. After ion irradiation, the resist is removed and a conventional functional lubricant is thereafter applied. The buff/wiping lubricant must be removed prior to resist deposition; otherwise the resist cannot be effectively applied.
In order that the buff/wiping lubricant be removable, a nonfunctional lubricant, preferably perfluoropolyether or polyphenoxytriphosphazene, is employed. This lubricant can be completely removed using a low-cost conventional degreasing process employing conventional solvents.
The protective carbon overcoat may be single or multiple layers of amorphous diamond-like carbon. It may further be hydrogenated or nitrogenated. In order that the carbon not be adversely affected by chemical reaction with the ions of the ion irradiation step, inert irradiation ions are employed. The ions are caused to impact the disk with a kinetic energy substantially less than 100 keV. This energy is insufficient to adversely affect the carbon overcoat, but is sufficient to reduce the remanence of the magnetic layers in proper dosages.
The carbon layer protects the magnetic layers during processing steps that occur once the disk has been removed from the sputtering chamber. It permits the use of a buff/wiping step prior to subsequent patterning steps. The lubricant prevents the disk from being scratched by the debris.
Alternatively, if a non-contacting stencil is used as the mask, a functional lubricant may be used prior to the buff/wiping step. The functional lubricant is preferably a perfluoropolyether lubricant having one or more functional groups and may be the lubricant conventionally used to lubricate finished magnetic disks for hard disk drives.